


Big Hero Sis

by Prineapple



Category: Big Hero 6 (2014)
Genre: Family, Gen
Language: English
Status: Completed
Published: 2014-12-07
Updated: 2014-12-14
Packaged: 2018-02-28 11:36:32
Rating: Teen And Up Audiences
Warnings: Graphic Depictions Of Violence
Chapters: 2
Words: 3,368
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/2731019
Author URL: https://archiveofourown.org/users/Prineapple/pseuds/Prineapple
Summary: <blockquote class="userstuff">
              <p>Hiro gets a pseudo-sis and immediately wants to return her. They bond...eventually.</p>
            </blockquote>





	1. Chapter 1

**Author's Note:**

> So I already posted this on FanFiction.net (My username is Vilva) and I have seen next to no OC stories here (Maybe I haven't been looking hard enough???). I looked at this site and saw how experienced and literate everyone was and I thought 'it would be really stupid of me to post my half-rate work on this coolios site'. So of course I did. Enjoy. Disclaimer: I don't own Big Hero 6.

Aunt Cass sighed tiredly and glanced back at the hunched over nephew who remained uncharacteristically quiet. "Hiro," she practically pleaded, "Please don't pout..."

"I'm not pouting," Hiro pouted, drawing his knees up to his chin. He glared at the unfinished pieces of robot he had long given up working on. "I'm expressing my feelings."

Baymax paused from clearing the table and turned toward Hiro before raising his finger and stating in his mechanical fashion, "Expression of emotion is advised as it clears possible antagonistic misunderstandings. However, it is also suggested that when stating emotions, one should also consider the opposing sides argu-"

"I'm satisfied with my care," Hiro growled, sliding from the wooden kitchen chair and stomping up the staircase.

Baymax made to follow him but Hiro slammed the door in his face. Aunt Cass sighed again and resumed washing the dishes.

Leaning against the wooden door, Hiro waited until he heard the mechanical hum of Baymax toddling down the stairs before slumping to the ground. He rubbed his forehead with a groan. How immature could he get, pouting and then slamming the door on his best friend?! Deep inside Hiro knew he was the one at fault and if anything he should have seen it coming. But instead of noticing how tired Aunt Cass had looked lately, Hiro had been completely wrapped up in the management of Big Hero 6.

"Some Hero," he muttered bitterly, "Can't even take care of his own family..."

At last, when the chilling cold of the wooden floorboards began to seep into his bones, Hiro stood up-and flopped down face-first onto his bed. When he ran out breath, he turned on his side. Hiro stared blankly at Tadashi's side of the room. Or what used to be Tadashi's side of the room.

Tadashi had always been somewhat of a neat freak so there hadn't been much to clean up. But now, what few posters had hung on the walls where taken down and the sheets were replaced with newer crispier ones. All of Tadashi's textbooks and manuals were stored in a cardboard box under Hiro's bed. Even the yellowed screen-wall that used to divide the room had been replaced by a new white one. Aunt Cass had even mentioned repainting the walls a more appealing color. It looked like a bedroom straight out of a interior decor magazine. Spotless and unlived in. Hiro hated it.

He turned on his side and faced his cluttered desk instead. Maybe if he ignored that part of the room it would still feel the same. Messy and...homey. Hiro wrapped himself deeper in his thoughts until it was all just another normal day with Aunt Cass moving around downstairs, the electric hum of Baymax trying to help, and the sound of footsteps as Tadashi crept up the stairs trying to not disturb Hiro-.

With a frustrated growl, Hiro pulled his pillow over his head. He would not think about it. He would not think about it. He could not think about it.

Hiro heard a sob that he didn't register as his own until he felt the dampness of tears rolling down his cheeks. "Dammit..." he whimpered, "Dammit all..."

He was supposed to be healing. He was supposed to have already accepted it. He should have gotten over it by now. So why?

"Why does he keep coming back?!" Hiro hissed to himself.

Everyone else, Honey Lemon, Fred, Wasabi, GoGo, Aunt Cass, heck even Baymax had gotten over it. They were moving on and he was left behind. It wasn't fair. He was the leader. He should be strong. He needed to be strong. It wasn't fair!

Letting out a yell, Hiro ripped the pillow off his head and launched it at his desk. It hit the wood with a dull thud causing some chaotically placed action figures and bolts to clatter to the floor.

Hiro was furious. Furious at himself for being unable to move on. And furious at everyone else for being able to.

His eyes darted around the room until they landed on Tadashi's baseball cap-black with an orange brim. On it where an embroidered S, F, and N. The San Fransiskyo Ninjas. Tadashi's favorite team.

Body moving before his mind, Hiro snatched up the cap and a pair of scissors. Maybe, just maybe, if he destroyed it then all these irrational feelings would leave. With a crazed smile plastered on his face, Hiro raised the scissors preparing to tear the cap to shreds-and stopped.

He couldn't do it. Hiro just couldn't. He was weak, so weak, for holding on. And he couldn't stop.

Scissors dropping to the floor, Hiro cradled the cap as a fresh wave of tears hit him. "What do I do?" he whispered to the cap, "I can't move on. I can't forget. It's hurting me and it's hurting everyone around me as well. What do I do Tadashi?"

Suddenly, Hiro's bedroom door burst open and Aunt Cass bolted inside, followed closely by Baymax. Aunt Cass glanced at the cap in Hiro's lap, her eyes widening. "Oh Hiro..." she whispered, at loss for words. Baymax shuffled past her and swept Hiro up in a cushioned hug. "There there," he said rocking side to side. "It will be alright." Hiro simply pressed his face against the robot's vinyl, avoiding Aunt Cass's gaze. He was surprised to feel a pair a second pair of significantly slimmer arms encircle him.

"Hiro," Aunt Cass's voice trembled with emotion, "I'm so so sorry...I thought you had fully accepted well you know. But...oh honey." Her grip tightened.

Hiro bit his lip. Why wasn't Aunt Cass mad at him for being so weak? And why was she apologizing?

Aunt Cass continued shakily, "Hiro I'm so sorry for not understanding and I know that I've already done some remodeling but.."

At this Hiro's eyes widened. Aunt Cass couldn't possibly be saying...

"They don't arrive until next month so I can still tell them no," Aunt Cass said firmly "I know the reason that I considered this in the first place was because we're short on money but I guess I can always take that loan Krei mentioned." Hiro was facing her now and she met his eyes with a grim gaze of determination. "I have always been too prideful but family comes first."

Hiro was ecstatic. This was perfect! Life would remain normal with just Aunt Cass, Baymax, Mochi, and him. He opened his mouth to let out a happy "Yes!".

But then he took a closer look at Aunt Cass. She had always been pretty but recently, stress and age had began to take over. Hiro spotted a couple of gray hairs as well as the faint worry line worn into her previously smooth brow. Dark circles had settled underneath her eyes and Aunt Cass's seemingly strong gaze flickered with worry.

Glancing down at the baseball cap in his lap, Hiro knew what he had to do.

"No," he said quietly, "I can't make you do that Aunt Cass." Aunt Cass's eyes widened in surprise as he continued.

"It's pretty obvious that I don't like the idea of someone else I don't know well living in the same room as me especially since...Tadashi's gone. But I can't just wallow in self-pity. I know that you also suffered Aunt Cass. Besides I read somewhere that change is good for the soul or something. So yeah, if it helps you, bring in all the boarders you. Just...not to many. And this sounds super sappy but uh yeah."

The entire time Hiro rambled Aunt Cass's lips had gradually curved into a smile. When he stopped and looked at her sheepishly, she beamed and hugged him even tighter.

"Thank you Hiro," Aunt Cass said happily before cautiously adding, "I think Tadashi would be proud."

Hiro froze and then relaxed before agreeing, "Yeah...and uh Baymax you can stop that now." The entire time, the robot had rocked Hiro back and forth. He now looked at the teen in his arms. "Are you alright Hiro?" he inquired. Wiping some excess tears with his shirt sleeve, Hiro sent him a watery smile. "Getting there."

Satisfied, Baymax, gently released the teen. Aunt Cass smiled softly at Hiro before ruffling his hair excitedly. "Oh I'm sure you two will get along just fine! In fact, I think she's going to the same college as you!"

Hiro' mouth dropped open in shock. "Wait it's a girl?!"


	2. She's Crazy

**Notes for the Chapter:**

> Disclaimer: Guess who doesn't own Big Hero 6? ME! Guess who does have an endless supply of Not-Quite-Christmas-Chocolate? ME AGAIN!  
> Thanks for reading!

One Month-ish later:

Hiro blew a stray piece of dark hair from his eyes and leaned back. Carefully he placed aside the small screwdriver on a tabletop covered with similar tools. "Alright," Hiro said, cracking his neck slightly, "Let's try that one more time!"

Baymax hummed mechanically in agreement before the small black cameras that served as his eyes lit up. A pale circle appeared on the robot's stomach and began to fill up, accompanied by the words Loading Video Conference . Hiro held his breath as the circle filled completely. For a moment nothing happened.

Slowly a glowing screen flickered to life. As it grew brighter, Hiro could just make out the outline of his bed and desk. Finally, the screen adjusted its focus, clearly showing Hiro's speakers on the side of Baymax's head cam to life, relaying the lively sounds of Aunt Cass's cafe downstairs. Allowing himself a small grin, Hiro continued, "Hookay Baymax. Try zooming in and scanning my desk."

With another click and whirl, Baymax did accordingly so. A light green grid appeared on the screen as the cameras began to zero in on different areas. "Material: plywood with metal bracings. Surface area: 216 square inches. Volume: 540 cubic inches. These are all approximations. Would you like me to conduct a more detailed scan?"

Hiro shook his head, and tapped his foot thoughtfully. "No that's okay. For now can you try telling me what exactly is inside my desk?"

"Affirmative." The grid changed to a bright blue. Outlines and labels began to appear. "Your desk contains 456 miniature bolts, 5 screwdrivers, 2 pairs of scissors, 15 reams of blueprint paper..." Baymax continued listing and categorizing random items. "...and one bag of corroding gummy bears." Hiro shrugged sheepishly at the somewhat accusing look Baymax sent him. "I'll clean that up later...?"

Rubbing his hands together with a nervous grin, Hiro rocked on the balls of his feet. Pulling out a stop watch, he gulped. "Alright buddy. Ready to do this?" Baymax tilted his head slightly. "Affirmative." Hiro nodded, "Okay. Baymax, make my bed."

From the speakers came a soft hum which Hiro knew to be the sound of Baymax inflating. The view point of the camera also began rise slowly. At last, the camera began to move slowly toward the direction of Hiro's bed-knocking down the new lamp Aunt Cass had recently purchased in the process. Whoops.

Hiro's attention was diverted when the camera reached his bed. He held his breath as two marshmallow-like arms reached forward and began adjusting the messy sheets. Glancing down quickly at his stopwatch, Hiro crossed his fingers. "C'mon..."

The arms began to pick up and fold random articles of clothing strewn haphazardly across the sheets. 0:55 With jerky movements, the arms began smoothing out the sheets. 1:15. Having tucked the sheets tightly in the sides of the bed, the arms moved to straighten, Hiro's many pillows. 1:45. Hiro gnawed his bottom lip as the arms reached for thicker blanket. 2:00. Wait 2:00? No. Way.

"AW YEAH!" Hiro crowed while fist-pumping, "Two minutes baby!"

Baymax merely tilted his head in an amused manner as the excited fifteen year old performed a victory dance similar to a seizure victim. "I fail to understand what a 'baby' has anything to do with two minutes." Hiro stopped dancing and scratched his neck, face flushing red. "Oh that. Uh I guess Fred is rubbing off on me..."

A loud chime sounded and Baymax straightened stating, "Command: Make Bed Complete." Hiro nodded happily and raised his hand in a closed fist. "Fist bump!" Baymax raised his fist as well and they both made their customary 'balalala' noise.

"Wow," Hiro commented looking at his now neat and tidy bed, "That's the cleanest I've ever seen my bed. Thanks buddy." Baymax replied, "Making beds make me a better healthcare companion." They were interrupted by a opening of Hiro's bedroom door as Aunt Cass strode in with Mochi at her heels. The camera turned toward her as she asked, "Baymax? What are you doing? And what was that loud noise-" Aunt Cass's eyes widened and she gasped. "My new lamp! Hiro!"

"Err Baymax, why don't you stop the call now?" Hiro said hurriedly. As the screen blacked-out he sighed in relief. "This isn't going to end well..." he muttered before perking up again. "But hey! Operation Doppelganger is a go! Better go record this." He raced toward his desktop but was stopped by a large growl emitting from his stomach.

Baymax lifted his finger but Hiro cut him off. "I know man I know. I'll go get something to eat. You should go charge too. Good job today and I'm satisfied with my care."

As the robot obediently toddled to his charging station, Hiro stretched and rubbed his eyes tiredly. Prying himself off his swivel chair, the teen stumbled out of his lab, the doors sliding closed behind him with a pleasant hum.

A glance at his stopwatch told him it was 4:30. The hallways were mostly empty, the majority of the students having gone home for the weekends. Stiffing a yawn, Hiro punched the elevator controls and stepped in. The customarily soothing elevator music filled his ears and it took all his willpower not to fall asleep.

When he reached the cafeteria at last, Hiro had to pinch himself a couple of times to remain standing. Working nonstop from 5:30-4:30 and skipping lunch could do that to you.

He spotted the majority of the gang sitting at one of the lunch tables. Seeing him, Honey Lemon waved and mouthed 'Finally!' Hiro rolled his eyes but couldn't conceal a small smile. He pointed to the cafeteria line and mouthed 'Join you later.' Honey Lemon nodded, catching the attention of Gogo and Wasabi who nodded and waved at Hiro.

At last, Hiro made his way over to the gang's table, his tray packed to the brim. He grunted out a "Hey guys" before attacking his chicken sandwich. Honey Lemon and Wasabi stared at him while Gogo merely raised an eyebrow. Spewing crumbs in the process, Hiro asked, "What?"

Honey Lemon giggled while Wasabi chuckled. "Puberty hitting you hard little man?" Wasabi teased. Hiro's cheeks flushed as he sputtered-causing more crumbs to fly out. Dodging the spray Wassabi whimpered. Wincing slightly and edging away, Gogo suggested, "Why don't you try talking after you're done eating." Hiro shrugged in apology and commenced wolfing down a generous slice of pizza.

The pile of food didn't stand a chance. Within minutes all that remained was a wad of wrappers and some apple cores. Hiro let out a sigh of contentment and then a loud burp. Heads turned towards the source causing Hiro to blush furiously. "Excuse me," he muttered while glaring at his friends who where desperately trying not to laugh.

Honey Lemon began to clean up Hiro's mess with a fond smile. Hiro's mouth opened, but she shook her head "Uh-uh-uh! Allow me!" Hiro shrugged and smiled saying, "Okay okay. And thanks Honey Lemon." Ruffling his hair slightly, the tall girl walked towards the trashcan.

Wasabi, looking much more relieved now that the mess was gone, said to Hiro, "So I'm guessing you skipped lunch again." In reply, Hiro waved his hand in a dismissive gesture. "Bah, who has time for lunch when we have science?" Wasabi chuckled but Gogo frowned slightly.

"You shouldn't skip lunch," she said sharply, "Your skinny enough as it is. Tadashi wouldn't want you to starve yourself even if you are saving the world."

At the mention of his brother's name Hiro's previously slouched posture went frigid. Wasabi cleared his throat nervously and glanced pointedly at Gogo who glared back. After a long silence Hire spoke, "He probably would've huh..."

Wasabi's jaw dropped as Hiro continued. "I guess I did get a bit too wrapped up in Operation Doppelganger. Thanks Gogo for reminding me." The teen finished with a small smile which Gogo awkwardly attempted to return.

As soon as, Hiro's attention was diverted by his phone, Wasabi tugged at Gogo's arm. Undaunted by her annoyed expression, he hissed, "What were you thinking?!" Gogo merely cracked her gum. "The kid's growing Wasabi. You'd be surprised. I don't think he needs anymore coddling." And with that, she pulled out her headphones and ignored Wasabi's dramatic flailing.

Honey Lemon returned from the trashcans and immediately sensed something had changed. "Sooo what did I miss?" she asked half-jokingly. "Puberty," Wasabi replied glumly. "Huh?" "Nothing."

A bit confused, Honey Lemon decided to switch to a different topic. "So Hiro how come Aunt Cass didn't pack you lunch today?" Hiro's expression soured and he shrugged, tapping away at his phone. "The boarder is coming tomorrow and she wants to get everything ready." Honey Lemon sat down next to Hiro.

"Ah, the one who's going to our college right? What's she like?" Wordlessly, Hiro brought up a conversation on his phone and slid it in Honey Lemon's direction. Puzzled she picked it up and read it.

From: CassHamada057@wooglemail.com

To: Sunnyday343@wooglemail.com 

Subject: Boarding

Hello Sunni,

Thank you very much for agreeing to board with us. As you know I have a cat, a nephew, and run a cafe as well. Again if any of these factors are a problem, please contact me ASAP. You replied earlier that you do not mind boarding with anyone else so if it is alright, you will be sharing a room with my nephew. I apologize in advance for the lack of space. Again thank you and we hope to see you soon!

Cass Hamada

Honey Lemon looked up at Hiro who was twiddling his thumbs. "Her name is very nice," she supplied. Hiro scowled slightly, "Yeah." Confused by his reaction, she swiped to later messages.

Reply: Sunnyday343@wooglemail.com

To: CassHamada057@wooglemail.com

Subject: Re: Boarding

Honey Lemon blinked, trying to take in the...colorful message. "Whoa," said Wasabi looking over her shoulder, "That's a lot of emojies." Gogo grunted in agreement.

Hiro groaned. "See? She's crazy!"

"Or she has a lot of free time," Wasabi suggested, prompting the teen to growl. "Fine! She's crazy and she has a lot of free time! And I'm living with her!" Honey Lemon dodged one of his flailing limbs as he waved dramatically to prove his point.

"Well..." she said cautiously, "She might be a bit strange but she seems nice..." Hiro opened his mouth to object but she said hastily, "I mean we all agree that this took quite some effort right? And she's just saying thank you." Gogo shook her head and cracked her gum. "Say what you want but she seems crazy enough to me." Honey Lemon glared at her before handing Hiro back his phone.

"Besides," Wasabi said, "I'm sure Aunt Cass won't let you live with anyone crazy. If she approves this chick then she's probably cool." Hiro frowned before sighing. "You're probably right. I'm probably just a bit ya know...tense." Sliding his phone into his pocket, he stood up and stretched. "Anyways, thanks guys. I needed that."

Gogo punched him lightly in the shoulder saying, "Don't worry. If she dares to mess with the leader of Big Hero 6-," She then cracked her knuckles ,"-then she's not even going to know what hit her." Hiro smiled a little and waved before jogging out of the cafeteria. The three college students watched him go.

As soon as Hiro was out of sight, Honey Lemon sighed and massaged her temples. "She's absolutely crazy." Wasabi groaned and dropped his head in his hands. "True that. I mean who spends that much time on something so small?" The girls looked at him. "Right, right."

**Notes for the Chapter:**

> I dun understand people who use a lot of emojis. I suppose they feel that I am emotionless. BUT DEEP DOWN I DO HAVE A HEART!!! ;( 3 D: D: D:
> 
>  
> 
>  
> 
> LOL. Nope.

**Author's Note:**

> Yes I did just try to flatter all of you.


End file.
